OFUNATO, Japan (CNN) -- Days after the earthquake and tsunami struck Japan, more than 7,500 people are still missing, and the number could likely rise.

Search and rescue teams are on hand in some areas-- helping with the hunt for survivors.

The relieved mayor of Ofunato greets U.S. and British rescue teams as they start their first full day of operations, but his city's condition could lie beyond their reach.

The tsunami came through Ofunato's narrow inlet with such force a tugboat was thrown several blocks, and cars were violently scattered for miles.

"The first thing is we find a place to search. We have map grids that are set up by the local emergency managers in the area. They give us an area to search. We split it up. We take coordinates. We go through the buildings, search it building by building- standing up or laying down," said Fairfax Co. Urban Search and Rescue Capt. Sam Gray.

The teams fan out, through mountains of rubble and teetering buildings, using every tool they brought.

Rescuers got word there was a note posted on a house that there was someone alive inside. They had the dog teams check it out, but the dogs didn't detect the scene of anyone alive.

"If you can hear me, knock three times!" yelled one of the rescue team members.

Listening devices and audio signal yielded nothing.

Residents who did escape the tsunami are in shock.

It was initially thought Tomuko Shida lost her husband in the disaster, but a translator says, "Her husband already died. She had stored in a box...She put it in a really high place. And when the storm came, she couldn't reach the box. She ran away first."

She's still looking for her husband's remains.

For those who did lose loved ones in this disaster, the final casualty count here may never be known.

"The way we're operating now there's still plenty of opportunity to find live victims. But as time goes on, those opportunities diminish," says Battalion Chief Chris Schaff of Virginia Task Force 1.

In many of these places, rescuers say they rely on local citizens, flagging them down to come and get a loved one out of a building or out of a pile of rubble.

One team member said that in Ofunato, whole families might have gone missing, and there might not be anyone even looking for them.